MM-10702 Moving plugins to use hashicorp go-plugin. (#8978)

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

model/plugin_status.go

@@ -10,24 +10,22 @@ import (
 
 const (
 	PluginStateNotRunning          = 0
-	PluginStateStarting            = 1
+	PluginStateStarting            = 1 // unused by server
 	PluginStateRunning             = 2
 	PluginStateFailedToStart       = 3
-	PluginStateFailedToStayRunning = 4
-	PluginStateStopping            = 5
+	PluginStateFailedToStayRunning = 4 // unused by server
+	PluginStateStopping            = 5 // unused by server
 )
 
 // PluginStatus provides a cluster-aware view of installed plugins.
 type PluginStatus struct {
-	PluginId      string `json:"plugin_id"`
-	ClusterId     string `json:"cluster_id"`
-	PluginPath    string `json:"plugin_path"`
-	State         int    `json:"state"`
-	IsSandboxed   bool   `json:"is_sandboxed"`
-	IsPrepackaged bool   `json:"is_prepackaged"`
-	Name          string `json:"name"`
-	Description   string `json:"description"`
-	Version       string `json:"version"`
+	PluginId    string `json:"plugin_id"`
+	ClusterId   string `json:"cluster_id"`
+	PluginPath  string `json:"plugin_path"`
+	State       int    `json:"state"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	Version     string `json:"version"`
 }
 
 type PluginStatuses []*PluginStatus